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Stability and biofouling behavior of plastic films in microalgae cultivation
- Yixuan WANG Chenghu YAN Wei CONG
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Chin. J. Process Eng.. 2020, 20(1):
74-83.
DOI: 10.12034/j.issn.1009-606X.219175
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The stability of six typical kinds of plastic films including polyethylene (PE), polypropylene (PP), ethylene/vinyl acetate (EVA), polyvinyl chloride (PVC), polyurethane (PU) and polyethylene terephthalate (PET) in NaClO, NaOH and HCl solutions and biofouling behavior in microalgae cultivation (Chlorella vulgaris) system were studied. The results showed that PVC film performed the poorest stability, and the transmittance decreased about 50% after immersing in NaClO, NaOH and HCl solutions. The transmittance of PU film and EVA film declined 10%?15% in NaClO and NaOH solutions, respectively. The transmittance of the other three kinds of plastic films has no significant change when immersed in NaClO, NaOH and HCl solutions for 24 h. Obvious microalgae biofouling behavior happened in six kinds of films, which was a typical biofilm formation process. Adhesion behavior of PVC surface was the most distinct, and the transmittance declined to about 0 on the 7th day, and the amount of adsorption solids increased with time and reached 3069 ?g/cm2 on the 45th day. However, the amount of adsorption solids on PU, EVA, PE, PP and PET film surface increased sharply and then decreased with time, the maximum amounts were 292, 375, 292, 194 and 236 ?g/cm2, respectively. The increase of chlorophyll content on the surface of the plastic films was not obvious in the first 4 d, which indicated that the initial stage of the adhesion was mainly the adhesion of protein and extracellular polymeric substances (EPS), and then microalgae cells began to adhere. The attachment of protein, EPS and microalgae cells on the plastic films was a typical biofilm formation process. The adhesion behavior of microalgae was affected by chemical structure and surface properties of the films, such as hydrophilicity, roughness and surface charge. For Chlorella vulgaris, polyolefin (PE, PP, etc.) and PET film surface with high hydrophilicity, low roughness and negatively charged will perform good anti-biofouling properties.